1. Field Of The Invention
The invention relates generally to probe-mounted sensors used to detect the level of a liquid in a chamber, such as oil in the crankcase of an engine. More particularly, the invention relates to an apparatus for mounting and orienting probe-mounted liquid-level sensing elements in a chamber.
2. Description Of The Art
It is known to detect liquid level by mounting sensing elements at the end of a probe inserted into a chamber containing a liquid. A common version employs two piezoelectric elements mounted with a space between them. An electrical voltage is applied to one element to cause it to vibrate ultrasonically. The vibration is transmitted through the space to the other piezoelectric element, causing it to vibrate and thereby generate a voltage. If the space between the members is filled with a liquid, the vibration will be transmitted more efficiently than if it is filled with air or another gas. A circuit measures the voltage level produced by the receiving piezoelectric element and, if the voltage level indicates the absence of the fluid in the space, produces a display, sounds an alarm or causes some other action such as shutting down the engine. Examples of such devices are found in U.S. Pat. Nos. 3,825,025, 3,851,333 and 4,964,090.
Sensing elements other than piezoelectric may also be employed. For example, analogous devices can be devised using optical transmission or electrical conduction through the space between a pair of optical elements or a pair of electrical terminals respectively to detect the presence of a liquid at the end of the probe. Alternatively, the sensing element could consist of a float mounted at the end of the probe whose movement makes and breaks an electrical circuit.
Such devices have posed a locational problem and an orientation problem. The locational problem arises because prior art devices employ a straight probe. Because the probe is straight, the opening for it in the wall of the chamber dictates the position of the probe mounting hole in the chamber wall, and that position may be undesirable for manufacturing or installation purposes. The orientation problem is that proper operation of the sensing elements often requires a particular rotational orientation of the probe. For example, with ultrasonic sensors, the ultrasonic vibration is best transmitted horizontally rather than vertically for proper measurement. If a float is used, the probe must be oriented so that the float is free to move vertically. In known devices, it is difficult to easily set and fix the correct rotational position of the probe. In those devices, the probe is directly threaded into an aperture in the chamber wall. Variations in relative thread alignment, in starting positions and in degree of tightening make it difficult to correctly orient the elements at the end of the probe.